Many of Snow Leopard's refinements are subtle

— -- Apple doesn't need to make a vista-sized leap on Friday, when it migrates from its Mac OS X Leopard operating system to Snow Leopard.

In the nearly two years since Leopard pounced onto the scene, it has elicited a far different reaction from the Mac faithful than Windows Vista has with the PC crowd. So, while Snow Leopard brings solid technological enhancements to Mac OS X, including built-in support for Microsoft Exchange, there was no need for the kind of major overhaul Microsoft will unleash with Windows 7 on Oct. 22.

In that sense, Snow Leopard isn't a must-have upgrade. There's not much new in the sizzle department. Many feature enrichments are modest, such as the ability to highlight text from a specific column in a PDF. The fine Safari 4 Web browser is also included, but you don't need Snow Leopard to get it. Apple does say the browser is faster and more crash resistant. (My iMac did crash once in my testing.)

Still, Snow Leopard should delight Mac fans, especially those who use Exchange at work. Leopard users can upgrade to Snow Leopard for just $29 (or $49 for a five-computer license), compared with the $129 it cost to go from the OS X Tiger to Leopard. The new operating system, which requires a Mac with an Intel processor, will also be preinstalled on new Macs.

Apple says there are hundreds of refinements and performance-boosting new technologies built into Snow Leopard, but many are under the hood. For example, Snow Leopard can make better use of the graphic chips in today's computers. It can also take advantage of the "64-bit" processors now built into all Macs, so applications will be able to make the most out of the processor and memory on such systems.

The new operating system was preinstalled on a MacBook Pro laptop that Apple supplied for testing. I also upgraded my own iMac. Highlights:

•Installation. It took an hour and seven minutes to upgrade the iMac. Though it went smoothly, I did get a post-installation notice that an old version of Parallels Desktop software on my Mac was incompatible. Snow Leopard takes up less space, so the new operating system gives back roughly 7 gigabytes of storage — enough to store thousands of digital photos. Apple says the installer now includes a "safe redo" to protect your data in the unlikely event that the power goes out during installation.